Some skills have synergy with each other, and matching them up will make them even more effective.
Let's take Fury for example. Fury increases your stats but forces you to take damage each time you fight.
So what if we pair Fury up with Reprisal, which increases your damage based on how much health you've lost? You can see where I'm going with this.
I see... Ahem! So what you're trying to say is that you can have skills excel beyond their original capacities through complementary matching of their advantages and disadvantages.
Or simply put, one can carefully study a skill's inherent drawbacks, if any, and turn them into advantages by utilizing their synergy with other skills!
Uh... Yes, "simply put." Why do I get the feeling you just got a lecture about this from a strategist?
Fill in Empty Slots First!
When you're inheriting skills, start by filling in the empty skill slots for the Hero who's receiving the skills. Assist skills and special skills are particularly worth prioritizing in this way.
Keep Synergy in Mind!
Sometimes, you can match together several different skills to create synergy between them. Look at the weapons and skills your Heroes have and see what you can come up with.
Example: Triangle Adept & Raven
"Raven" tomes are effective against colorless enemies, and you can pair these with the Triangle Adept skill to do even more damage when the Hero has the advantage. Triangle Adept will also trigger when fighting enemies the Hero has a color advantage against, making this combination favorable in two different matchups.
Example: Reprisal & Fury
This combination matches skills from the Vengeance family together with Fury. The former increases the damage of a Hero's special skill whenever that Hero takes damage, while the latter has the property of depleting the Hero's health whenever they fight. As the Hero will keep taking damage the more they fight, the damage bonus from Reprisal (30% of the value of maximum HP minus current HP) will continue to increase.